The calcium-activated chloride channel anoctamin 1 acts as a heat sensor in nociceptive neurons

Thermosensitivity of TREK K2P channels is controlled by a PKA switch and depends on the microtubular network

Temperature sensing is an essential component of animal perception and enables individuals to avoid painful or lethal temperatures. Many temperature sensors in central and peripheral neurons are ion channels. Here, we focus on the thermosensitive TREK/TRAAK subfamily of K2P channels-the only known K+ selective thermosensitive channels. The C-terminal domain is essential for the temperature activation of TREK channels, but the mechanism of temperature sensation and the nature of the temperature sensor are unknown. We studied the thermosensitivity of representatives of all K2P channel subfamilies and identified TREK-1 and TREK-2 as the only thermosensitive K2P channels, while TRAAK, the third member of the mechano-gated subfamily, showed no temperature dependence. We transferred the thermosensitivity of TREK-1 to TRAAK channels by exchanging the C-termini, demonstrating that the C-terminal domain is sufficient to confer thermosensitivity. By gradually truncating the C-terminus, we isolated a specific temperature responsive element (TRE) consisting of 18 amino acids that constitutes a unique feature in mammalian thermosensitive channels. Within this TRE lie both the binding domain for microtubule associated protein 2 (MAP2) and the PKA phosphorylation site. Pharmacological disruption of the microtubular network as well as the loss of the MAP2 binding site suppressed the temperature response, and PKA activation completely abolished temperature sensitivity. Thus, the connection to the microtubular network enables the thermosensitivity of TREK channels, which is not intrinsic to the channel itself, while the PKA-mediated phosphorylation status acts as a switch that determines if TREK channels are thermosensitive at all.

Regulatory Action of Calcium and Calcium Channels in Pain Pathways

Calcium ions (Ca2+) and Ca2+ channels are pivotal in the regulation of pain pathways and serve as key regulators of neuronal excitability and neurotransmitter release. We review the different types of Ca2+ channels involved in pain processing, including voltage-gated Ca2+ channels (VGCCs), such as L-, N-, P/Q-, and T-type channels. Each subtype is intricately involved in different aspects of pain perception, from acute pain signaling to the development and maintenance of chronic pain states. In addition, the roles of transient receptor potential (TRP) channels, particularly TRPV1 and TRPA1, are discussed in the context of their contribution to chronic pain. Advances in Ca2+ imaging techniques, particularly through genetically encoded Ca2+ indicators (GECIs), such as GCaMPs, have provided unprecedented insight into the dynamic role of Ca2+ channels in pain pathways. These efforts have deepened our understanding of Ca2+ channels and suggest novel therapeutic targets for more effective pain management strategies within Ca2+ channels.

Arteries are finely tuned thermosensors regulating myogenic tone and blood flow

In response to changing blood pressure, arteries adjust their caliber to control blood flow. This vital autoregulatory property, termed vascular myogenic tone, stabilizes downstream capillary pressure. Here, we reveal that tissue temperature, combined with intraluminal pressure, critically determines myogenic tone. Heating steeply activates tone in skeletal muscle, gut, brain, and skin arteries with temperature coefficients (Q10) of ~11 to 20. Each of these tissues has a distinct resting temperature, and we find that arterial thermosensitivity is tuned to this temperature, making myogenic tone sensitive to small thermal fluctuations. Interestingly, temperature and intraluminal pressure are sensed largely independently and the signals integrated to trigger myogenic tone. We demonstrate that thermosensitive channels TRPV1 and TRPM4 mediate heat-induced tone in skeletal muscle arteries with discrete temperature sensitivities. Similarly, TRPM4 contributes to heat-induced tone in gut and brain arteries. The half-maximal responses occur at approximately 31 °C for TRPV1 and 33 °C for TRPM4. Variations in tissue temperature are known to alter blood fluidity and therefore vascular conductance; remarkably, thermosensitive tone counterbalances this effect, thus protecting capillary integrity and fluid balance. In conclusion, thermosensitive myogenic tone is a fundamental homeostatic mechanism regulating tissue perfusion.

Neuroimmune interactions: The bridge between inflammatory bowel disease and the gut microbiota

BACKGROUND

The multidimensional regulatory mechanism of the gut-brain-immune axis in the context of inflammatory bowel disease (IBD) has garnered significant attention, particularly regarding how intestinal microbiota finely regulates immune responses through immune cells and sensory neurons.

MAIN BODY

Metabolites produced by intestinal microbiota influence the phenotype switching of immune cells via complex signalling pathways, thereby modulating their anti-inflammatory and pro-inflammatory functions during intestinal inflammation. Furthermore, sensory neurons exhibit heightened sensitivity to microbial-derived signals, which is essential for preserving intestinal balance and controlling pathological inflammation by integrating peripheral environmental signals with local immune responses. The dynamic equilibrium between immune cells and the neuroimmunoregulation mediated by sensory neurons collectively sustains immune homeostasis within the intestine. However, this coordination mechanism is markedly disrupted under the pathological conditions associated with IBD.

CONCLUSION

An in-depth exploration of the interactions among immune cells, gut microbiota and sensory neurons may yield significant insights into the pathological mechanisms underlying IBD and guide the creation of new treatment approaches.

KEY POINTS

The gut microbiota regulates the gut-brain-immune axis, modulating neuroimmune interactions in IBD. Microbiota-derived metabolites influence immune cells, thereby affecting neurons. Neurons secrete mediators, enabling bidirectional neuroimmune communication essential for intestinal homeostasis. Disruptions contribute to IBD, offering therapeutic targets.

Transmembrane protein 16A in the digestive diseases: A review of its physiology, pharmacology, and therapeutic opportunities

Transmembrane protein 16A (TMEM16A) is a Ca2+-activated Cl- channel that is widely expressed in the digestive system, and numerous compounds have been developed for targeting TMEM16A. This review summarizes the current state of knowledge of physiological and pathological roles of TMEM16A in the digestive system, and discuss the potential therapeutic uses and challenges of TMEM16A modulators, with a focus on their selectivity, potency and molecular mechanisms as well as off-target tissue effects. We propose that TMEM16A exerts physiological and pathological roles in a tissue-specific or disease-specific way, and try to establish the idea that TMEM16A modulators are promising for therapeutic uses in digestive diseases such as secretory diarrhea, gastrointestinal motility disorders, and hepatobiliary and pancreatic diseases, as well as various cancers.

ANO1: central role and clinical significance in non-neoplastic and neoplastic diseases

Anoctamin 1 (ANO1), also known as TMEM16A, is a multifunctional protein that serves as a calcium-activated chloride channel (CaCC). It is ubiquitously expressed across various tissues, including epithelial cells, smooth muscle cells, and neurons, where it is integral to physiological processes such as epithelial secretion, smooth muscle contraction, neural conduction, and cell proliferation and migration. Dysregulation of ANO1 has been linked to the pathogenesis of numerous diseases. Extensive research has established its involvement in non-neoplastic conditions such as asthma, hypertension, and gastrointestinal (GI) dysfunction. Moreover, ANO1 has garnered significant attention for its role in the development and progression of cancers, including head and neck cancer, breast cancer, and lung cancer, where its overexpression correlates with increased tumor growth, metastasis, and poor prognosis. Additionally, ANO1 regulates multiple signaling pathways, including the epidermal growth factor receptor (EGFR) pathway, the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway, and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway, among others. These pathways are pivotal in regulating cell proliferation, migration, and invasion. Given its central role in these processes, ANO1 has emerged as a promising diagnostic biomarker and therapeutic target. Recent advancements in ANO1 research have highlighted its potential in disease diagnosis and treatment. Strategies targeting ANO1, such as small molecule modulators or gene-silencing techniques, have shown preclinical promise in both non-neoplastic and neoplastic diseases. This review explores the latest findings in ANO1 research, focusing on its mechanistic involvement in disease progression, its regulation, and its therapeutic potential. Modulating ANO1 activity may offer novel therapeutic strategies for effectively treating ANO1-associated diseases.

Anoctamins mediate polymodal sensory perception and larval metamorphosis in a non-vertebrate chordate

The ocean represents a complex sensory environment, which acts as a crucible of evolution for polymodal sensory perception. The cellular and molecular bases of polymodal sensory perception in a marine environment remain enigmatic. Here, we use Ca2+ imaging and quantitative behavioral analysis to show that in the tunicate Ciona intestinalis, two members of the evolutionarily conserved anoctamin family (Tmem16E/Ano5 and Tmem16F/Ano6) are required for sensing chemosensory and mechanosensory metamorphic cues. We find that they modulate neuronal excitability and Ca2+ response kinetics in the primary sensory neurons and axial columnar cells of the papillae. Chemogenetic perturbations suggest that Ano5 and Ano6 act downstream of the primary sensory transducer molecules. Using pharmacology, we show that Ano5 and Ano6 cooperate with the inositol 1,4,5-trisphosphate (IP3) receptor and calcium release-activated channels (CRACs) to modulate tail regression. Our results establish Ano5 and Ano6 as players in the zooplanktonic molecular toolkit that controls polymodal sensory perception in aquatic environments.

Na V 1.8/Na V 1.9 double deletion mildly affects acute pain responses in mice

ABSTRACT

The 2 tetrodotoxin-resistant (TTXr) voltage-gated sodium channel subtypes Na V 1.8 and Na V 1.9 are important for peripheral pain signaling. As determinants of sensory neuron excitability, they are essential for the initial transduction of sensory stimuli, the electrogenesis of the action potential, and the release of neurotransmitters from sensory neuron terminals. Na V 1.8 and Na V 1.9, which are encoded by SCN10A and SCN11A , respectively, are predominantly expressed in pain-sensitive (nociceptive) neurons localized in the dorsal root ganglia (DRG) along the spinal cord and in the trigeminal ganglia. Mutations in these genes cause various pain disorders in humans. Gain-of-function missense variants in SCN10A result in small fiber neuropathy, while distinct SCN11A mutations cause, i. a., congenital insensitivity to pain, episodic pain, painful neuropathy, and cold-induced pain. To determine the impact of loss-of-function of both channels, we generated Na V 1.8/Na V 1.9 double knockout (DKO) mice using clustered regularly interspaced short palindromic repeats/Cas-mediated gene editing to achieve simultaneous gene disruption. Successful knockout of both channels was verified by whole-cell recordings demonstrating the absence of Na V 1.8- and Na V 1.9-mediated Na + currents in Na V 1.8/Na V 1.9 DKO DRG neurons. Global RNA sequencing identified significant deregulation of C-LTMR marker genes as well as of pain-modulating neuropeptides in Na V 1.8/Na V 1.9 DKO DRG neurons, which fits to the overall only moderately impaired acute pain behavior observed in DKO mice. Besides addressing the function of both sodium channels in pain perception, we further demonstrate that the null-background is a very valuable tool for investigations on the functional properties of individual human disease-causing variants in Na V 1.8 or Na V 1.9 in their native physiological environment.

Interaction between thermosensitive TRP channels and anoctamin 1

Some thermosensitive transient receptor potential (TRP) channels form a protein complex with anoctamin 1 (ANO1, also called TMEM16A). TRP channels have high calcium permeability, and the calcium entering cells through TRP channel activation activates ANO1, a calcium-activated chloride channel, involved in many physiological and pathological conditions. The physiological significance of TRP channels is often mediated by their ability to activate ANO1, which controls chloride flux across the plasma membrane. This review summarizes the latest understanding on the interactions between ANO1 and thermosensitive TRP channels, including TRPV1, TRPV3, and TRPV4, which are involved in pain sensitization in primary sensory neurons, proliferation and migration of human keratinocytes, and fluid secretion such as sweat, respectively.

Anoctamin-1 is a core component of a mechanosensory anion channel complex in C. elegans

Mechanotransduction channels are widely expressed in both vertebrates and invertebrates, mediating various physiological processes such as touch, hearing and blood-pressure sensing. While previously known mechanotransduction channels in metazoans are primarily cation-selective, we identified Anoctamin-1 (ANOH-1), the C. elegans homolog of mammalian calcium-activated chloride channel ANO1/TMEM16A, as an essential component of a mechanosensory channel complex that contributes to the nose touch mechanosensation in C. elegans. Ectopic expression of either C. elegans or human Anoctamin-1 confers mechanosensitivity to touch-insensitive neurons, suggesting a cell-autonomous role of ANOH-1/ANO1 in mechanotransduction. Additionally, we demonstrated that the mechanosensory function of ANOH-1/ANO1 relies on CIB (calcium- and integrin- binding) proteins. Thus, our results reveal an evolutionarily conserved chloride channel involved in mechanosensory transduction in metazoans, highlighting the importance of anion channels in mechanosensory processes.

Targeting TMEM16A ion channels suppresses airway hyperreactivity, inflammation, and remodeling in an experimental Guinea pig asthma model

Asthma is a chronic inflammatory disease characterized by airway hyperresponsiveness, inflammation, and remodeling. Calcium (Ca2+)-activated chloride (Cl-) channels, such as TMEM16A, are inferred to be involved in asthma. Therefore, the present study investigated the therapeutic potential of TMEM16A inhibition in a guinea pig model of ovalbumin (OVA)-induced allergic asthma. Guinea pigs were treated with a specific blocker, CaCCinh-A01 (10 μM), administered via inhalation. A significant reduction in cough reflex sensitivity and specific airway resistance was observed in animals treated with CaCCinh-A01, highlighting its potential to improve airway function. Despite a reduction in ciliary beating frequency (CBF), CaCCinh-A01 reduced airway mucus viscosity by decreasing the production of mucin-5AC (MUC5AC). The nonspecific reduction in the Th1/Th2 cytokine spectrum following CaCCinh-A01 treatment indicated the suppression of airway inflammation. Additionally, markers associated with airway remodeling were diminished, suggesting that CaCCinh-A01 may counteract structural changes in airway tissues. Therefore, inhibition appears to mitigate the pathological aspects of asthma, including airway hyperresponsiveness, inflammation, and remodeling. However, further studies are required to comprehensively evaluate the potential of TMEM16A as a therapeutic target for asthma.

Anoctamin 1, a multi-modal player in pain and itch

Anoctamin 1 (ANO1/TMEM16A) encodes a Ca2+-activated Cl- channel. Among ANO1's many physiological functions, it plays a significant role in mediating nociception and itch. ANO1 is activated by intracellular Ca2+ and depolarization. Additionally, ANO1 is activated by heat above 44 °C, suggesting heat as another activation stimulus. ANO1 is highly expressed in nociceptors, indicating a role in nociception. Conditional Ano1 ablation in dorsal root ganglion (DRG) neurons results in a reduction in acute thermal pain, as well as thermal and mechanical allodynia or hyperalgesia evoked by inflammation or nerve injury. Pharmacological interventions also lead to a reduction in nocifensive behaviors. ANO1 is functionally linked to the bradykinin receptor and TRPV1. Bradykinin stimulates ANO1 via IP3-mediated Ca2+ release from intracellular stores, whereas TRPV1 stimulates ANO1 via a combination of Ca2+ influx and release. Nerve injury causes upregulation of ANO1 expression in DRG neurons, which is blocked by ANO1 antagonists. Due to its role in nociception, strong and specific ANO1 antagonists have been developed. ANO1 is also expressed in pruritoceptors, mediating Mas-related G protein-coupled receptors (Mrgprs)-dependent itch. The activation of ANO1 leads to chloride efflux and depolarization due to high intracellular chloride concentrations, causing pain and itch. Thus, ANO1 could be a potential target for the development of new drugs treating pain and itch.

Gene Expression Shifts in Emperor Penguin Adaptation to the Extreme Antarctic Environment

Gene expression can accelerate ecological divergence by rapidly tweaking the response of an organism to novel environments, with more divergent environments exerting stronger selection and supposedly, requiring faster adaptive responses. Organisms adapted to extreme environments provide ideal systems to test this hypothesis, particularly when compared to related species with milder ecological niches. The Emperor penguin (Aptenodytes forsteri) is the only endothermic vertebrate breeding in the harsh Antarctic winter, in stark contrast with the less cold-adapted sister species, the King penguin (A. patagonicus). Assembling the first de novo transcriptomes and analysing multi-tissue (brain, kidney, liver, muscle, skin) RNA-Seq data from natural populations of both species, we quantified the shifts in tissue-enhanced genes, co-expression gene networks, and differentially expressed genes characterising Emperor penguin adaptation to the extreme Antarctic. Our analyses revealed the crucial role played by muscle and liver in temperature homeostasis, fasting, and whole-body energy metabolism (glucose/insulin regulation, lipid metabolism, fatty acid beta-oxidation, and blood coagulation). Repatterning at the regulatory level appears as more important in the brain of the Emperor penguin, showing the lowest signature of differential gene expression, but the largest co-expression gene network shift. Nevertheless, over-expressed genes related to mTOR signalling in the brain and the liver support their central role in cold and fasting responses. Besides contributing to understanding the genetics underlying complex traits, like body energy reservoir management, our results provide a first insight into the role of gene expression in adaptation to one of the most extreme environmental conditions endured by an endotherm.

Human heat sensation: A randomized crossover trial

Sensing of noxious heat has been reported to be mediated by TRPV1, TRPA1, TRPM3, and ANO1 in mice, and this is redundant so that the loss of one receptor is at least partially compensated for by others. We have established an infusion-based human heat pain model. Heat-induced pain probed with antagonists for the four receptors did not match the redundancy found in mice. In healthy participants, only TRPV1 contributes to the detection of noxious heat; none of the other three receptors are involved. TRPV1 inhibition reduced the pain at all noxious temperatures, which can also be seen as an increase in the temperature that causes a particular level of pain. However, even if the TRPV1-dependent shift in heat detection is about 1°C, at the end of the temperature ramp to 52°C, most heat-induced pain remains unexplained. This difference between species reopens the quest for the molecular safety net for the detection of noxious heat in humans.

Mechanical and thermal stimulation for studying the somatosensory system: a review on devices and methods

The somatosensory system is widely studied to understand its functioning mechanisms. Multiple tests, based on different devices and methods, have been performed not only on humans but also on animals andex-vivomodels. Depending on the nature of the sample under analysis and on the scientific aims of interest, several solutions for experimental stimulation and for investigations on sensation or pain have been adopted. In this review paper, an overview of the available devices and methods has been reported, also analyzing the representative values adopted during literature experiments. Among the various physical stimulations used to study the somatosensory system, we focused only on mechanical and thermal ones. Based on the analysis of their main features and on literature studies, we pointed out the most suitable solution for humans, rodents, andex-vivomodels and investigation aims (sensation and pain).

The Estrogen Receptor Alpha Regulates the Sex-dependent Expression and Pronociceptive Role of Bestrophin-1 in Neuropathic Rats

Bestrophin-1, a calcium-activated chloride channel (CaCC), is involved in neuropathic pain; however, it is unclear whether it has a dimorphic role in female and male neuropathic rats. This study investigated if 17β-estradiol and estrogen receptor alpha (ERα) activation regulate bestrophin-1 activity and expression in neuropathic rats. Neuropathic pain was induced by L5-spinal nerve transection (SNT). Intrathecal administration of CaCCinh-A01 (.1-1 µg), a CaCC blocker, reversed tactile allodynia induced by SNT in female but not male rats. In contrast, T16Ainh-A01, a selective anoctamin-1 blocker, had an equal antiallodynic effect in both sexes. SNT increased bestrophin-1 protein expression in injured L5 dorsal root ganglia (DRG) in female rats but decreased bestrophin-1 protein in L5 DRG in male rats. Ovariectomy prevented the antiallodynic effect of CaCCinh-A01, but 17β-estradiol replacement restored it. The effect of CaCCinh-A01 was prevented by intrathecal administration of MPP, a selective ERα antagonist, in rats with and without prior hormonal manipulation. In female rats with neuropathy, ovariectomy prevented the increase in bestrophin-1 and ERα protein expression, while 17β-estradiol replacement allowed for an increase in both proteins in L5 DRG. Furthermore, ERα antagonism (with MPP) prevented the increase in bestrophin-1 and ERα protein expression. Finally, ERα activation with PPT, an ERα selective activator, induced the antiallodynic effect of CaCCinh-A01 in neuropathic male rats and prevented the reduction in bestrophin-1 protein expression in L5 DRG. In summary, data suggest ERα activation is necessary for bestrophin-1's pronociceptive action to maintain neuropathic pain in female rats. PERSPECTIVE: The mechanisms involved in neuropathic pain differ between male and female animals. Our data suggest that ERα is necessary for expression and function of bestrophin-1 in neuropathic female but not male rats. Data support the idea that a therapeutic approach to relieving neuropathic pain must be based on patient's gender.

Prostaglandin E2 depolarises sensory axons in vitro in an ANO1 and Nav1.8 dependent manner

Prostaglandin E2 (PGE2) is a major contributor to inflammatory pain hyperalgesia, however, the extent to which it modulates the activity of nociceptive axons is incompletely understood. We developed and characterized a microfluidic cell culture model to investigate sensitisation of the axons of dorsal root ganglia neurons. We show that application of PGE2 to fluidically isolated axons leads to sensitisation of their responses to depolarising stimuli. Interestingly the application of PGE2 to the DRG axons elicited a direct and persistent spiking activity propagated to the soma. Both the persistent activity and the membrane depolarisation in the axons are abolished by the EP4 receptor inhibitor and a blocker of cAMP synthesis. Further investigated into the mechanisms of the spiking activity showed that the PGE2 evoked depolarisation was inhibited by Nav1.8 sodium channel blockers but was refractory to the application of TTX or zatebradine. Interestingly, the depolarisation of axons was blocked by blocking ANO1 channels with T16Ainh-A01. We further show that PGE2-elicited axonal responses are altered by the changes in chloride gradient within the axons following treatment with bumetanide a Na-K-2Cl cotransporter NKCC1 inhibitor, but not by VU01240551 an inhibitor of potassium-chloride transporter KCC2. Our data demonstrate a novel role for PGE2/EP4/cAMP pathway which culminates in a sustained depolarisation of sensory axons mediated by a chloride current through ANO1 channels. Therefore, using a microfluidic culture model, we provide evidence for a potential dual function of PGE2 in inflammatory pain: it sensitises depolarisation-evoked responses in nociceptive axons and directly triggers action potentials by activating ANO1 and Nav1.8 channels.

Spinal bestrophin-1 and anoctamin-1 channels have a pronociceptive role in the tactile allodynia induced by REM sleep deprivation in rats

Bestrophin-1 and anoctamin-1 are members of the calcium-activated chloride channels (CaCCs) family and are involved in inflammatory and neuropathic pain. However, their role in pain hypersensitivity induced by REM sleep deprivation (REMSD) has not been studied. This study aimed to determine if anoctamin-1 and bestrophin-1 are involved in the pain hypersensitivity induced by REMSD. We used the multiple-platform method to induce REMSD. REM sleep deprivation for 48 h induced tactile allodynia and a transient increase in corticosterone concentration at the beginning of the protocol (12 h) in female and male rats. REMSD enhanced c-Fos and α2δ-1 protein expression but did not change activating transcription factor 3 (ATF3) and KCC2 expression in dorsal root ganglia and dorsal spinal cord. Intrathecal injection of CaCCinh-A01, a non-selective bestrophin-1 blocker, and T16Ainh-A01, a specific anoctamin-1 blocker, reverted REMSD-induced tactile allodynia. However, T16Ainh-A01 had a higher antiallodynic effect in male than female rats. In addition, REMSD increased bestrophin-1 protein expression in DRG but not in DSC in male and female rats. In marked contrast, REMSD decreased anoctamin-1 protein expression in DSC but not in DRG, only in female rats. Bestrophin-1 and anoctamin-1 promote pain and maintain tactile allodynia induced by REM sleep deprivation in both male and female rats, but their expression patterns differ between the sexes.

Insights into the function and regulation of the calcium-activated chloride channel TMEM16A

The TMEM16A channel, a member of the TMEM16 protein family comprising chloride (Cl-) channels and lipid scramblases, is activated by the free intracellular Ca2+ increments produced by inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release after GqPCRs or Ca2+ entry through cationic channels. It is a ubiquitous transmembrane protein that participates in multiple physiological functions essential to mammals' lives. TMEM16A structure contains two identical 10-segment monomers joined at their transmembrane segment 10. Each monomer harbours one independent hourglass-shaped pore gated by Ca2+ ligation to an orthosteric site adjacent to the pore and controlled by two gates. The orthosteric site is created by assembling negatively charged glutamate side chains near the pore´s cytosolic end. When empty, this site generates an electrostatic barrier that controls channel rectification. In addition, an isoleucine-triad forms a hydrophobic gate at the boundary of the cytosolic vestibule and the inner side of the neck. When the cytosolic Ca2+ rises, one or two Ca2+ ions bind to the orthosteric site in a voltage (V)-dependent manner, thus neutralising the electrostatic barrier and triggering an allosteric gating mechanism propagating via transmembrane segment 6 to the hydrophobic gate. These coordinated events lead to pore opening, allowing the Cl- flux to ensure the physiological response. The Ca2+-dependent function of TMEM16A is highly regulated. Anions with higher permeability than Cl- facilitate V dependence by increasing the Ca2+ sensitivity, intracellular protons can replace Ca2+ and induce channel opening, and phosphatidylinositol 4,5-bisphosphate bound to four cytosolic sites likely maintains Ca2+ sensitivity. Additional regulation is afforded by cytosolic proteins, most likely by phosphorylation and protein-protein interaction mechanisms.

TMC6 functions as a GPCR-like receptor to sense noxious heat via Gαq signaling

Thermosensation is vital for the survival, propagation, and adaption of all organisms, but its mechanism is not fully understood yet. Here, we find that TMC6, a membrane protein of unknown function, is highly expressed in dorsal root ganglion (DRG) neurons and functions as a Gαq-coupled G protein-coupled receptor (GPCR)-like receptor to sense noxious heat. TMC6-deficient mice display a substantial impairment in noxious heat sensation while maintaining normal perception of cold, warmth, touch, and mechanical pain. Further studies show that TMC6 interacts with Gαq via its intracellular C-terminal region spanning Ser780 to Pro810. Specifically disrupting such interaction using polypeptide in DRG neurons, genetically ablating Gαq, or pharmacologically blocking Gαq-coupled GPCR signaling can replicate the phenotype of TMC6 deficient mice regarding noxious heat sensation. Noxious heat stimulation triggers intracellular calcium release from the endoplasmic reticulum (ER) of TMC6- but not control vector-transfected HEK293T cell, which can be significantly inhibited by blocking PLC or IP3R. Consistently, noxious heat-induced intracellular Ca2+ release from ER and action potentials of DRG neurons largely reduced when ablating TMC6 or blocking Gαq/PLC/IP3R signaling pathway as well. In summary, our findings indicate that TMC6 can directly function as a Gαq-coupled GPCR-like receptor sensing noxious heat.

The anoctamins: Structure and function

When activated by increase in intracellular Ca2+, anoctamins (TMEM16 proteins) operate as phospholipid scramblases and as ion channels. Anoctamin 1 (ANO1) is the Ca2+-activated epithelial anion-selective channel that is coexpressed together with the abundant scramblase ANO6 and additional intracellular anoctamins. In salivary and pancreatic glands, ANO1 is tightly packed in the apical membrane and secretes Cl-. Epithelia of airways and gut use cystic fibrosis transmembrane conductance regulator (CFTR) as an apical Cl- exit pathway while ANO1 supports Cl- secretion mainly by facilitating activation of luminal CFTR and basolateral K+ channels. Under healthy conditions ANO1 modulates intracellular Ca2+ signals by tethering the endoplasmic reticulum, and except of glands its direct secretory contribution as Cl- channel might be small, compared to CFTR. In the kidneys ANO1 supports proximal tubular acid secretion and protein reabsorption and probably helps to excrete HCO3-in the collecting duct epithelium. However, under pathological conditions as in polycystic kidney disease, ANO1 is strongly upregulated and may cause enhanced proliferation and cyst growth. Under pathological condition, ANO1 and ANO6 are upregulated and operate as secretory channel/phospholipid scramblases, partly by supporting Ca2+-dependent processes. Much less is known about the role of other epithelial anoctamins whose potential functions are discussed in this review.

The role of anoctamin 1 in liver disease

Liver diseases include all types of viral hepatitis, alcoholic liver disease (ALD), nonalcoholic fatty liver disease (NAFLD), cirrhosis, liver failure (LF) and hepatocellular carcinoma (HCC). Liver disease is now one of the leading causes of disease and death worldwide, which compels us to better understand the mechanisms involved in the development of liver diseases. Anoctamin 1 (ANO1), a calcium-activated chloride channel (CaCC), plays an important role in epithelial cell secretion, proliferation and migration. ANO1 plays a key role in transcriptional regulation as well as in many signalling pathways. It is involved in the genesis, development, progression and/or metastasis of several tumours and other diseases including liver diseases. This paper reviews the role and molecular mechanisms of ANO1 in the development of various liver diseases, aiming to provide a reference for further research on the role of ANO1 in liver diseases and to contribute to the improvement of therapeutic strategies for liver diseases by regulating ANO1.

Kalium channelrhodopsins effectively inhibit neurons

The analysis of neural circuits has been revolutionized by optogenetic methods. Light-gated chloride-conducting anion channelrhodopsins (ACRs)-recently emerged as powerful neuron inhibitors. For cells or sub-neuronal compartments with high intracellular chloride concentrations, however, a chloride conductance can have instead an activating effect. The recently discovered light-gated, potassium-conducting, kalium channelrhodopsins (KCRs) might serve as an alternative in these situations, with potentially broad application. As yet, KCRs have not been shown to confer potent inhibitory effects in small genetically tractable animals. Here, we evaluated the utility of KCRs to suppress behavior and inhibit neural activity in Drosophila, Caenorhabditis elegans, and zebrafish. In direct comparisons with ACR1, a KCR1 variant with enhanced plasma-membrane trafficking displayed comparable potency, but with improved properties that include reduced toxicity and superior efficacy in putative high-chloride cells. This comparative analysis of behavioral inhibition between chloride- and potassium-selective silencing tools establishes KCRs as next-generation optogenetic inhibitors for in vivo circuit analysis in behaving animals.

Cuprorivaite/hardystonite/alginate composite hydrogel with thermionic effect for the treatment of peri-implant lesion

Peri-implant lesion is a grave condition afflicting numerous indi-viduals with dental implants. It results from persistent periodontal bacteria accumulation causing inflammation around the implant site, which can primarily lead to implant loosening and ultimately the implant loss. Early-stage peri-implant lesions exhibit symptoms akin to gum disease, including swelling, redness and bleeding of the gums surrounding the implant. These signs indicate infection and inflammation of the peri-implant tissues, which may result in bone loss and implant failure. To address this problem, a thermionic strategy was applied by designing a cuprorivaite-hardystonite bioceramic/alginate composite hydrogel with photothermal and Cu/Zn/Si multiple ions releasing property. This innovative approach creates a thermionic effect by the release of bioactive ions (Cu2+ and Zn2+ and SiO 3 2 - ) from the composite hydrogel and the mild heat environment though the photothermal effect of the composite hydrogel induced by near-infrared light irradiation. The most distinctive advantage of this thermionic effect is to substantially eliminate periodontal pathogenic bacteria and inhibit inflammation, while simultaneously enhance peri-implant osseointegration. This unique attribute renders the use of this composite hydrogel highly effective in significantly improving the survival rate of implants after intervention in peri-implant lesions, which is a clinical challenge in periodontics. This study reveals application potential of a new biomaterial-based approach for peri-implant lesion, as it not only eliminates the infection and inflammation, but also enhances the osteointegration of the dental implant, which provides theoretical insights and practical guidance to prevent and manage early-stage peri-implant lesion using bioactive functional materials.

A mouse DRG genetic toolkit reveals morphological and physiological diversity of somatosensory neuron subtypes

Dorsal root ganglia (DRG) somatosensory neurons detect mechanical, thermal, and chemical stimuli acting on the body. Achieving a holistic view of how different DRG neuron subtypes relay neural signals from the periphery to the CNS has been challenging with existing tools. Here, we develop and curate a mouse genetic toolkit that allows for interrogating the properties and functions of distinct cutaneous targeting DRG neuron subtypes. These tools have enabled a broad morphological analysis, which revealed distinct cutaneous axon arborization areas and branching patterns of the transcriptionally distinct DRG neuron subtypes. Moreover, in vivo physiological analysis revealed that each subtype has a distinct threshold and range of responses to mechanical and/or thermal stimuli. These findings support a model in which morphologically and physiologically distinct cutaneous DRG sensory neuron subtypes tile mechanical and thermal stimulus space to collectively encode a wide range of natural stimuli.

Pathophysiological Roles of Ion Channels in Epidermal Cells, Immune Cells, and Sensory Neurons in Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by the rapid abnormal growth of skin cells in the epidermis, driven by an overactive immune system. Consequently, a complex interplay among epidermal cells, immune cells, and sensory neurons contributes to the development and progression of psoriasis. In these cellular contexts, various ion channels, such as acetylcholine receptors, TRP channels, Ca2+ release-activated channels, chloride channels, and potassium channels, each serve specific functions to maintain the homeostasis of the skin. The dysregulation of ion channels plays a major role in the pathophysiology of psoriasis, affecting various aspects of epidermal cells, immune responses, and sensory neuron signaling. Impaired function of ion channels can lead to altered calcium signaling, inflammation, proliferation, and sensory signaling, all of which are central features of psoriasis. This overview summarizes the pathophysiological roles of ion channels in epidermal cells, immune cells, and sensory neurons during early and late psoriatic processes, thereby contributing to a deeper understanding of ion channel involvement in the interplay of psoriasis and making a crucial advance toward more precise and personalized approaches for psoriasis treatment.

Function and Regulation of the Calcium-Activated Chloride Channel Anoctamin 1 (TMEM16A)

Various human tissues express the calcium-activated chloride channel Anoctamin 1 (ANO1), also known as TMEM16A. ANO1 allows the passive chloride flux that controls different physiological functions ranging from muscle contraction, fluid and hormone secretion, gastrointestinal motility, and electrical excitability. Overexpression of ANO1 is associated with pathological conditions such as hypertension and cancer. The molecular cloning of ANO1 has led to a surge in structural, functional, and physiological studies of the channel in several tissues. ANO1 is a homodimer channel harboring two pores - one in each monomer - that work independently. Each pore is activated by voltage-dependent binding of two intracellular calcium ions to a high-affinity-binding site. In addition, the binding of phosphatidylinositol 4,5-bisphosphate to sites scattered throughout the cytosolic side of the protein aids the calcium activation process. Furthermore, many pharmacological studies have established ANO1 as a target of promising compounds that could treat several illnesses. This chapter describes our current understanding of the physiological roles of ANO1 and its regulation under physiological conditions as well as new pharmacological compounds with potential therapeutic applications.

Temperature-Dependent Activation of Thermosensitive Transient Receptor Potential Channels

Temperature detection is essential for the survival and perpetuation of any species. Thermoreceptors in the skin sense the body temperature and also the temperatures of the ambient air and the objects. In 1997, Dr. David Julius and his colleagues found that a receptor expressed in small-diameter primary sensory neurons was activated by capsaicin (the pungent chemical in hot pepper). This receptor was also activated by temperature above 42 °C. That was the first time that a thermal receptor in primary sensory neurons has been identified. This receptor is named transient receptor potential vanilloid 1 (TRPV1). Now, 11 thermosensitive TRP channels are known. In this chapter, we summarize the reports and analyze thermosensitive TRP channels in a variety of ways to clarify the activation mechanisms by which temperature changes are sensed.

Researches of calcium-activated chloride channel ANO1 intervening amyotrophic lateral sclerosis progression by activating EGFR and CaMKII signaling

BACKGROUND

ANO1 is closely correlated with the activation of EGFR and CaMKII, while EGFR and CaMKII show low activation in amyotrophic lateral sclerosis (ALS) models. Therefore, we designed experiments to verify that ANO1 may play a protective role on motor neurons in ALS by activating EGFR and CaMKII.

METHODS

The expression changes of ANO1, EGFR, CaMKII, pEGFR, and pCaMKII, cell survival status, and apoptosis were studied by western blot, real-time quantitative PCR, immunofluorescence, immunohistochemistry, CCK-8, and flow cytometry. The role of ANO1 in the ALS model by activating EGFR and CaMKII was studied by applying corresponding activators, inhibitors, gene silencing, and overexpression.

RESULTS

In hSOD1G93A transgenic animals and cell lines, low expression of ANO1 and low activation of EGFR and CaMKII were identified. ANO1 expression decreased gradually with the progression of ALS. Overexpression of ANO1 in the hSOD1G93A cell line and primary neurons of hSOD1G93A transgenic mice increased cell viability and decreased cell apoptosis. After the application of ANO1 inhibitor CaCC-inhA01 in hSOD1G93A cell line and primary neurons of hSOD1G93A transgenic mice, EGFR activator EGF and CaMKII activator Carbachol, increased cell viability and reduced cell apoptosis. After ANO1 was overexpressed in the hSOD1G93A cell line and primary neurons of hSOD1G93A transgenic mice, EGFR inhibitor AEE788 and CaMKII inhibitor KN93 decreased cell viability and increased cell apoptosis.

CONCLUSIONS

Our results suggest that ANO1 plays an important role in the survival of ALS motor neurons. ANO1 can increase cell activity and reduce apoptosis by activating EGFR and CaMKII signals.

TMEM16A ion channel: A novel target for cancer treatment

Cancer draws attention owing to the high morbidity and mortality. It is urgent to develop safe and effective cancer therapeutics. The calcium-activated chloride channel TMEM16A is widely distributed in various tissues and regulates physiological functions. TMEM16A is abnormally expressed in several cancers and associate with tumorigenesis, metastasis, and prognosis. Knockdown or inhibition of TMEM16A in cancer cells significantly inhibits cancer development. Therefore, TMEM16A is considered as a biomarker and therapeutic target for some cancers. This work reviews the cancers associated with TMEM16A. Then, the molecular mechanism of TMEM16A overexpression in cancer was analyzed, and the possible signal transduction mechanism of TMEM16A regulating cancer development was summarized. Finally, TMEM16A inhibitors with anticancer effect and their anticancer mechanism were concluded. We hope to provide new ideas for pharmacological studies on TMEM16A in cancer.

Ion Channel Genes in Painful Neuropathies

Neuropathic pain (NP) is a typical symptom of peripheral nerve disorders, including painful neuropathy. The biological mechanisms that control ion channels are important for many cell activities and are also therapeutic targets. Disruption of the cellular mechanisms that govern ion channel activity can contribute to pain pathophysiology. The voltage-gated sodium channel (VGSC) is the most researched ion channel in terms of NP; however, VGSC impairment is detected in only <20% of painful neuropathy patients. Here, we discuss the potential role of the other peripheral ion channels involved in sensory signaling (transient receptor potential cation channels), neuronal excitation regulation (potassium channels), involuntary action potential generation (hyperpolarization-activated cyclic nucleotide-gated channels), thermal pain (anoctamins), pH modulation (acid sensing ion channels), and neurotransmitter release (calcium channels) related to pain and their prospective role as therapeutic targets for painful neuropathy.

Dysregulation of TMEM16A impairs oviductal transport of embryos

Ectopic pregnancy is an acute abdominalgia in obstetrics and gynecology, especially in fallopian tubal pregnancy. The ion channel protein transmembrane protein 16A (TMEM16A) is widely distributed in various tissues, even in the oviduct. In this study, we showed that TMEM16A was expressed in the human fallopian tube and was upregulated in patients with tubal pregnancy. By measuring isolated fallopian tube tissues, we found that TMEM16A was involved in regulating not only the contraction of muscle strips but also the beat frequency of cilia. In addition, pharmacological activation or inhibition of TMEM16A could lead to retention of embryos in oviducts. Moreover, the embryos in oviducts were delayed in development and some of them had malformations and deletions. The total number of embryos in the oviducts and uterus was significantly less than that of the control group. Furthermore, we detected changes in the level of m6A methylation, where the relevant writers and readers were reduced in tubal tissues from tubal pregnancies. In m6A mRNA methylation, writers catalyze the addition of methyl groups to cytosine residues and readers bind to the methyl groups and affect gene translation. In human fallopian tube epithelial cell line FTE187, we found that interference with methyltransferase 3 (METTL3) expression increased TMEM16A, suggesting that TMEM16A might be regulated by m6A methylation. In general, our study revealed a novel regulatory point for embryo transport and development, introducing a new role for the diagnosis and treatment of tubal pregnancy.NEW & NOTEWORTHY The ion channel protein TMEM16A is expressed in the epithelium and smooth muscle of the human fallopian tube and is upregulated in patients with tubal pregnancy. TMEM16A is involved in regulating the smooth muscle contraction and the cilia beating. Dysregulated TMEM16A may result in embryo retention in the oviduct and delayed early embryo development. Our study reveals a new regulatory point for embryo transport and development.

TMEM16A partners with mTOR to influence pathways of cell survival, proliferation, and migration in cholangiocarcinoma

Expression of transmembrane protein 16 A (TMEM16A), a calcium activated chloride channel, is elevated in some human cancers and impacts tumor cell proliferation, metastasis, and patient outcome. Evidence presented here uncovers a molecular synergy between TMEM16A and mechanistic/mammalian target of rapamycin (mTOR), a serine-threonine kinase that is known to promote cell survival and proliferation in cholangiocarcinoma (CCA), a lethal cancer of the secretory cells of bile ducts. Analysis of gene and protein expression in human CCA tissue and CCA cell line detected elevated TMEM16A expression and Cl- channel activity. The Cl- channel activity of TMEM16A impacted the actin cytoskeleton and the ability of cells to survive, proliferate, and migrate as revealed by pharmacological inhibition studies. The basal activity of mTOR, too, was elevated in the CCA cell line compared with the normal cholangiocytes. Molecular inhibition studies provided further evidence that TMEM16A and mTOR were each able to influence the regulation of the other's activity or expression respectively. Consistent with this reciprocal regulation, combined TMEM16A and mTOR inhibition produced a greater loss of CCA cell survival and migration than their individual inhibition alone. Together these data reveal that the aberrant TMEM16A expression and cooperation with mTOR contribute to a certain advantage in CCA.NEW & NOTEWORTHY This study points to the dysregulation of transmembrane protein 16 A (TMEM16A) expression and activity in cholangiocarcinoma (CCA), the inhibition of which has functional consequences. Dysregulated TMEM16A exerts an influence on the regulation of mechanistic/mammalian target of rapamycin (mTOR) activity. Moreover, the reciprocal regulation of TMEM16A by mTOR demonstrates a novel connection between these two protein families. These findings support a model in which TMEM16A intersects the mTOR pathway to regulate cell cytoskeleton, survival, proliferation, and migration in CCA.

KCNE1 does not shift TMEM16A from a Ca2+ dependent to a voltage dependent Cl- channel and is not expressed in renal proximal tubule

The TMEM16A (ANO1) Cl^- channel is activated by Ca²⁺ in a voltage-dependent manner. It is broadly expressed and was shown to be also present in renal proximal tubule (RPT). KCNQ1 is an entirely different K⁺ selective channel that forms the cardiac I_KS potassium channel together with its ß-subunit KCNE1. Surprisingly, KCNE1 has been claimed to interact with TMEM16A, and to be required for activation of TMEM16A in mouse RPT. Interaction with KCNE1 was reported to switch TMEM16A from a Ca2²⁺-dependent to a voltage-dependent ion channel. Here we demonstrate that KCNE1 is not expressed in mouse RPT. TMEM16A expressed in RPT is activated by angiotensin II and ATP in a KCNE1-independent manner. Coexpression of KCNE1 does not change TMEM16A to a voltage gated Cl^- channel and Ca²⁺-dependent regulation of TMEM16A is fully maintained in the presence of KCNE1. While overexpressed KCNE1 slightly affects Ca²⁺-dependent regulation of TMEM16A, the data provide no evidence for KCNE1 being an auxiliary functional subunit for TMEM16A.

Glutamate-releasing BEST1 channel is a new target for neuroprotection against ischemic stroke with wide time window

Many efforts have been made to understand excitotoxicity and develop neuroprotectants for the therapy of ischemic stroke. The narrow treatment time window is still to be solved. Given that the ischemic core expanded over days, treatment with an extended time window is anticipated. Bestrophin 1 (BEST1) belongs to a bestrophin family of calcium-activated chloride channels. We revealed an increase in neuronal BEST1 expression and function within the peri-infarct from 8 to 48 h after ischemic stroke in mice. Interfering the protein expression or inhibiting the channel function of BEST1 by genetic manipulation displayed neuroprotective effects and improved motor functional deficits. Using electrophysiological recordings, we demonstrated that extrasynaptic glutamate release through BEST1 channel resulted in delayed excitotoxicity. Finally, we confirmed the therapeutic efficacy of pharmacological inhibition of BEST1 during 6-72 h post-ischemia in rodents. This delayed treatment prevented the expansion of infarct volume and the exacerbation of neurological functions. Our study identifies the glutamate-releasing BEST1 channel as a potential therapeutic target against ischemic stroke with a wide time window.

ANO1-downregulation induced by schisandrathera D: a novel therapeutic target for the treatment of prostate and oral cancers

Anoctamin 1 (ANO1), a drug target for various cancers, including prostate and oral cancers, is an intracellular calcium-activated chloride ion channel that plays various physiopathological roles, especially in the induction of cancer growth and metastasis. In this study, we tested a novel compound isolated from Schisandra sphenanthera, known as schisandrathera D, for its inhibitory effect on ANO1. Schisandrathera D dose-dependently suppressed the ANO1 activation-mediated decrease in fluorescence of yellow fluorescent protein; however, it did not affect the adenosine triphosphate-induced increase in the intracellular calcium concentration or forskolin-induced cystic fibrosis transmembrane conductance regulator activity. Specifically, schisandrathera D gradually decreased the levels of ANO1 protein and significantly reduced the cell viability in ANO1-expressing cells when compared to those in ANO1-knockout cells. These effects could be attributed to the fact that schisandrathera D displayed better binding capacity to ANO1 protein than the previously known ANO1 inhibitor, Ani9. Finally, schisandrathera D increased the levels of caspase-3 and cleaved poly (ADP-ribose) polymerase 1, thereby indicating that its anticancer effect is mediated through apoptosis. Thus, this study highlights that schisandrathera D, which reduces ANO1 protein levels, has apoptosis-mediated anticancer effects in prostate and oral cancers, and thus, can be further developed into an anticancer agent.

Daidzein attenuated paclitaxel-induced neuropathic pain via the down-regulation of TRPV1/P2Y and up-regulation of Nrf2/HO-1 signaling

Paclitaxel (PTX) is an anti-microtubule agent, used for the treatment of various types of cancers; however, it produces painful neuropathy which limits its use. Many neuroprotective agents have been introduced to mitigate PTX-induced neuropathic pain (PINP), but they pose many adverse effects. The purpose of this study was to evaluate the pharmacological characteristics of soy isoflavone, and daidzein (DZ) in attenuating PINP. At the beginning of the investigation, the effect of DZ was confirmed through behavioral analysis, as it reduced pain hypersensitivity. Moreover, changes in the histological parameters were reversed by DZ administration along with vascular permeability. PTX administration upregulated transient receptor potential vanilloid 1 (TRPV1) channels and purinergic receptors (P2Y), contributing to hyperalgesia; but administration of DZ downregulated the TRPV1 and P2Y, thus reducing hyperalgesia. DZ increased nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), playing a pivotal role in the activation of the antioxidant pathway. DZ also decreased neuronal apoptosis by decreasing caspase-3 and Bcl2-associated X-protein (Bax), while simultaneously, increasing Bcl-2. PTX administration produced severe DNA damage, which was mitigated by DZ. Similarly, DZ administration resulted in inhibition of neuroinflammation by increasing antioxidant enzymes and reducing oxidative stress markers. PTX caused increased in production of pro-inflammatory mediators such as the cytokines production, while DZ inhibited the pro-inflammatory mediators. Additionally, in silico pharmacokinetic and toxicodynamic study of DZ was also conducted. In summary, DZ demonstrated significant neuroprotective activity against PTX induced neuropathic pain.

Arteries are finely tuned thermosensors regulating myogenic tone and blood flow

In response to changing blood pressure, arteries adjust their caliber to control perfusion. This vital autoregulatory property, termed vascular myogenic tone, stabilizes downstream capillary pressure. We discovered that tissue temperature critically determines myogenic tone. Heating steeply activates tone in skeletal muscle, gut, brain and skin arteries with temperature coefficients ( Q 10 ) of ∼11-20. Further, arterial thermosensitivity is tuned to resting tissue temperatures, making myogenic tone sensitive to small thermal fluctuations. Interestingly, temperature and intraluminal pressure are sensed largely independently and integrated to trigger myogenic tone. We show that TRPV1 and TRPM4 mediate heat-induced tone in skeletal muscle arteries. Variations in tissue temperature are known to alter vascular conductance; remarkably, thermosensitive tone counterbalances this effect, thus protecting capillary integrity and fluid balance. In conclusion, thermosensitive myogenic tone is a fundamental homeostatic mechanism regulating tissue perfusion.

One-Sentence Summary

Arterial blood pressure and temperature are integrated via thermosensitve ion channels to produce myogenic tone.

A DRG genetic toolkit reveals molecular, morphological, and functional diversity of somatosensory neuron subtypes

Mechanical and thermal stimuli acting on the skin are detected by morphologically and physiologically distinct sensory neurons of the dorsal root ganglia (DRG). Achieving a holistic view of how this diverse neuronal population relays sensory information from the skin to the central nervous system (CNS) has been challenging with existing tools. Here, we used transcriptomic datasets of the mouse DRG to guide development and curation of a genetic toolkit to interrogate transcriptionally defined DRG neuron subtypes. Morphological analysis revealed unique cutaneous axon arborization areas and branching patterns of each subtype. Physiological analysis showed that subtypes exhibit distinct thresholds and ranges of responses to mechanical and/or thermal stimuli. The somatosensory neuron toolbox thus enables comprehensive phenotyping of most principal sensory neuron subtypes. Moreover, our findings support a population coding scheme in which the activation thresholds of morphologically and physiologically distinct cutaneous DRG neuron subtypes tile multiple dimensions of stimulus space.

A Novel Role of Uricosuric Agent Benzbromarone in BK Channel Activation and Reduction of Airway Smooth Muscle Contraction

The uricosuric drug benzbromarone, widely used for treatment of gout, hyperpolarizes the membrane potential of airway smooth muscle cells, but how it works remains unknown. Here we show a novel role of benzbromarone in activation of large conductance calcium-activated K+ channels. Benzbromarone results in dose-dependent activation of macroscopic big potassium (BK) currents about 1.7- to 14.5-fold with an EC50 of 111 μM and shifts the voltage-dependent channel activation to a more hyperpolarizing direction about 10 to 54 mV in whole-cell patch clamp recordings. In single-channel recordings, benzbromarone decreases single BKα channel closed dwell time and increases the channel open probability. Coexpressing β1 subunit also enhances BK activation by benzbromarone with an EC50 of 67 μM and a leftward shift of conductance-voltage (G-V) curve about 44 to 138 mV. Site-directed mutagenesis reveals that a motif of three amino acids 329RKK331 in the cytoplasmic linker between S6 and C-terminal regulator of potassium conductance (RCK) gating ring mediates the pharmacological activation of BK channels by benzbromarone. Further ex vivo assay shows that benzbromarone causes reduction of tracheal strip contraction. Taken together, our findings demonstrate that uricosuric benzbromarone activates BK channels through molecular mechanism of action involving the channel RKK motif of S6-RCK linker. Pharmacological activation of BK channel by benzbromarone causes reduction of tracheal strip contraction, holding a repurposing potential for asthma and pulmonary arterial hypertension or BK channelopathies. SIGNIFICANCE STATEMENT: We describe a novel role of uricosuric agent benzbromarone in big potassium (BK) channel activation and relaxation of airway smooth muscle contraction. In this study, we find that benzbromarone is an activator of the large-conductance Ca2+- and voltage-activated K+ channel (BK channel), which serves numerous cellular functions, including control of smooth muscle contraction. Pharmacological activation of BK channel by the FDA-approved drug benzbromarone may hold repurposing potential for treatment of asthma and pulmonary arterial hypertension or BK channelopathies.

The role of Transmembrane Protein 16A (TMEM16A) in pulmonary hypertension

Transmembrane protein 16A (TMEM16A), a member of the TMEM16 family, is the molecular basis of Ca2+-activated chloride channels (CaCCs) and is involved in a variety of physiological and pathological processes. Previous studies have focused more on respiratory-related diseases and tumors. However, recent studies have identified an important role for TMEM16A in cardiovascular diseases, especially in pulmonary hypertension. TMEM16A is expressed in both pulmonary artery smooth muscle cells and pulmonary artery endothelial cells and is involved in the development of pulmonary hypertension. This paper presents the structure and function of TMEM16A, the pathogenesis of pulmonary hypertension, and highlights the role and mechanism of TMEM16A in pulmonary hypertension, summarizing the controversies in this field and taking into account hypertension and portal hypertension, which have similar pathogenesis. It is hoped that the unique role of TMEM16A in pulmonary hypertension will be illustrated and provide ideas for research in this area.

Inhibition of ANO1 by Cis- and Trans-Resveratrol and Their Anticancer Activity in Human Prostate Cancer PC-3 Cells

Anoctamin1 (ANO1), a calcium-activated chloride channel, is involved in the proliferation, migration, and invasion of various cancer cells including head and neck squamous cell carcinoma, lung cancer, and prostate cancer. Inhibition of ANO1 activity or downregulation of ANO1 expression in these cancer cells is known to exhibit anticancer effects. Resveratrol, a natural polyphenol abundant in wines, grapes, berries, soybeans, and peanuts, shows a wide variety of biological effects including anti-inflammatory, antioxidant, and anticancer activities. In this study, we investigated the effects of two stereoisomers of resveratrol on ANO1 activity and found that cis- and trans-resveratrol inhibited ANO1 activity with different potencies. Cis- and trans-resveratrol inhibited ANO1 channel activity with IC₅₀ values of 10.6 and 102 μM, respectively, and had no significant effect on intracellular calcium signaling at 10 and 100 μM, respectively. In addition, cis-resveratrol downregulated mRNA and protein expression levels of ANO1 more potently than trans-resveratrol in PC-3 prostate cancer cells. Cis- and trans-resveratrol significantly reduced cell proliferation and cell migration in an ANO1-dependent manner, and both resveratrol isomers strongly increased caspase-3 activity, PARP cleavage, and apoptotic sub-G1 phase ratio in PC-3 cells. These results revealed that cis-resveratrol is a potent inhibitor of ANO1 and exhibits ANO1-dependent anticancer activity against human metastatic prostate cancer PC-3 cells.

Bestrophin-1 Participates in Neuropathic Pain Induced by Spinal Nerve Transection but not Spinal Nerve Ligation

Previous studies have reported that L5/L6 spinal nerve ligation (SNL), but not L5 spinal nerve transection (SNT), enhances anoctamin-1 in injured and uninjured dorsal root ganglia (DRG) of rats suggesting some differences in function of the type of nerve injury. The role of bestrophin-1 in these conditions is unknown. The aim of this study was to investigate the role of bestrophin-1 in rats subjected to L5 SNT and L5/L6 SNL. SNT up-regulated bestrophin-1 protein expression in injured L5 and uninjured L4 DRG at day 7, whereas it enhanced GAP43 mainly in injured, but also in uninjured DRG. In contrast, SNL enhanced GAP43 at day 1 and 7, while bestrophin-1 expression increased only at day 1 after nerve injury. Accordingly, intrathecal injection of the bestrophin-1 blocker CaCC_inh-A01 (1-10 µg) reverted SNT- or SNL-induced tactile allodynia in a concentration-dependent manner. Intrathecal injection of CaCC_inh-A01 (10 µg) prevented SNT-induced upregulation of bestrophin-1 and GAP43 at day 7. In contrast, CaCC_inh-A01 did not affect SNL-induced up-regulation of GAP43 nor bestrophin-1. Bestrophin-1 was mainly expressed in small- and medium-size neurons in naïve rats, while SNT increased bestrophin-1 immunoreactivity in CGRP+, but not in IB4+ neuronal cells in DRG. Intrathecal injection of bestrophin-1 plasmid (pCMVBest) induced tactile allodynia and increased bestrophin-1 expression in DRG and spinal cord in naïve rats. CaCC_inh-A01 reversed bestrophin-1 overexpression-induced tactile allodynia and restored bestrophin-1 expression. Our data suggest that bestrophin-1 plays a relevant role in neuropathic pain induced by SNT, but not by SNL. PERSPECTIVE: SNT, but not SNL, up-regulates bestrophin-1 and GAP43 protein expression in injured L5 and uninjured L4 DRG. SNT increases bestrophin-1 immunoreactivity in CGRP+ neurons in DRG. Bestrophin-1 overexpression induces allodynia. CaCCinh-A01 reduces allodynia and restores bestrophin-1 expression. Our data suggest bestrophin-1 is differentially regulated depending on the neuropathic pain model.

Amplification of olfactory signals by Anoctamin 9 is important for mammalian olfaction

Sensing smells of foods, prey, or predators determines animal survival. Olfactory sensory neurons in the olfactory epithelium (OE) detect odorants, where cAMP and Ca2+ play a significant role in transducing odorant inputs to electrical activity. Here we show Anoctamin 9, a cation channel activated by cAMP/PKA pathway, is expressed in the OE and amplifies olfactory signals. Ano9-deficient mice had reduced olfactory behavioral sensitivity, electro-olfactogram signals, and neural activity in the olfactory bulb. In line with the difference in olfaction between birds and other vertebrates, chick ANO9 failed to respond to odorants, whereas chick CNGA2, a major transduction channel, showed greater responses to cAMP. Thus, we concluded that the signal amplification by ANO9 is important for mammalian olfactory transduction.

Modulating cell signalling in vivo with magnetic nanotransducers

Weak magnetic fields offer nearly lossless transmission of signals within biological tissue. Magnetic nanomaterials are capable of transducing magnetic fields into a range of biologically relevant signals in vitro and in vivo. These nanotransducers have recently enabled magnetic control of cellular processes, from neuronal firing and gene expression to programmed apoptosis. Effective implementation of magnetically controlled cellular signalling relies on careful tailoring of magnetic nanotransducers and magnetic fields to the responses of the intended molecular targets. This primer discusses the versatility of magnetic modulation modalities and offers practical guidelines for selection of appropriate materials and field parameters, with a particular focus on applications in neuroscience. With recent developments in magnetic instrumentation and nanoparticle chemistries, including those that are commercially available, magnetic approaches promise to empower research aimed at connecting molecular and cellular signalling to physiology and behaviour in untethered moving subjects.

Peripheral Ion Channel Genes Screening in Painful Small Fiber Neuropathy

Neuropathic pain is a characteristic feature of small fiber neuropathy (SFN), which in 18% of the cases is caused by genetic variants in voltage-gated sodium ion channels. In this study, we assessed the role of fifteen other ion channels in neuropathic pain. Patients with SFN (n = 414) were analyzed for ANO1, ANO3, HCN1, KCNA2, KCNA4, KCNK18, KCNN1, KCNQ3, KCNQ5, KCNS1, TRPA1, TRPM8, TRPV1, TRPV3 and TRPV4 variants by single-molecule molecular inversion probes-next-generation sequencing. These patients did not have genetic variants in SCN3A, SCN7A-SCN11A and SCN1B-SCN4B. In twenty patients (20/414, 4.8%), a potentially pathogenic heterozygous variant was identified in an ion-channel gene (ICG). Variants were present in seven genes, for two patients (0.5%) in ANO3, one (0.2%) in KCNK18, two (0.5%) in KCNQ3, seven (1.7%) in TRPA1, three (0.7%) in TRPM8, three (0.7%) in TRPV1 and two (0.5%) in TRPV3. Variants in the TRP genes were the most frequent (n = 15, 3.6%), partly in patients with high mean maximal pain scores VAS = 9.65 ± 0.7 (n = 4). Patients with ICG variants reported more severe pain compared to patients without such variants (VAS = 9.36 ± 0.72 vs. VAS = 7.47 ± 2.37). This cohort study identified ICG variants in neuropathic pain in SFN, complementing previous findings of ICG variants in diabetic neuropathy. These data show that ICG variants are central in neuropathic pain of different etiologies and provides promising gene candidates for future research.

Modality specific roles for metabotropic GABAergic signaling and calcium induced calcium release mechanisms in regulating cold nociception

Calcium (Ca2+) plays a pivotal role in modulating neuronal-mediated responses to modality-specific sensory stimuli. Recent studies in Drosophila reveal class III (CIII) multidendritic (md) sensory neurons function as multimodal sensors regulating distinct behavioral responses to innocuous mechanical and nociceptive thermal stimuli. Functional analyses revealed CIII-mediated multimodal behavioral output is dependent upon activation levels with stimulus-evoked Ca2+ displaying relatively low vs. high intracellular levels in response to gentle touch vs. noxious cold, respectively. However, the mechanistic bases underlying modality-specific differential Ca2+ responses in CIII neurons remain incompletely understood. We hypothesized that noxious cold-evoked high intracellular Ca2+ responses in CIII neurons may rely upon Ca2+ induced Ca2+ release (CICR) mechanisms involving transient receptor potential (TRP) channels and/or metabotropic G protein coupled receptor (GPCR) activation to promote cold nociceptive behaviors. Mutant and/or CIII-specific knockdown of GPCR and CICR signaling molecules [GABA B -R2, Gαq, phospholipase C, ryanodine receptor (RyR) and Inositol trisphosphate receptor (IP3R)] led to impaired cold-evoked nociceptive behavior. GPCR mediated signaling, through GABA B -R2 and IP3R, is not required in CIII neurons for innocuous touch evoked behaviors. However, CICR via RyR is required for innocuous touch-evoked behaviors. Disruptions in GABA B -R2, IP3R, and RyR in CIII neurons leads to significantly lower levels of cold-evoked Ca2+ responses indicating GPCR and CICR signaling mechanisms function in regulating Ca2+ release. CIII neurons exhibit bipartite cold-evoked firing patterns, where CIII neurons burst during rapid temperature change and tonically fire during steady state cold temperatures. GABA B -R2 knockdown in CIII neurons resulted in disorganized firing patterns during cold exposure. We further demonstrate that application of GABA or the GABA B specific agonist baclofen potentiates cold-evoked CIII neuron activity. Upon ryanodine application, CIII neurons exhibit increased bursting activity and with CIII-specific RyR knockdown, there is an increase in cold-evoked tonic firing and decrease in bursting. Lastly, our previous studies implicated the TRPP channel Pkd2 in cold nociception, and here, we show that Pkd2 and IP3R genetically interact to specifically regulate cold-evoked behavior, but not innocuous mechanosensation. Collectively, these analyses support novel, modality-specific roles for metabotropic GABAergic signaling and CICR mechanisms in regulating intracellular Ca2+ levels and cold-evoked behavioral output from multimodal CIII neurons.

Reduced Expression of TMEM16A Impairs Nitric Oxide-Dependent Cl− Transport in Retinal Amacrine Cells

Postsynaptic cytosolic Cl⁻ concentration determines whether GABAergic and glycinergic synapses are inhibitory or excitatory. We have shown that nitric oxide (NO) initiates the release of Cl⁻ from acidic internal stores into the cytosol of retinal amacrine cells (ACs) thereby elevating cytosolic Cl⁻. In addition, we found that cystic fibrosis transmembrane conductance regulator (CFTR) expression and Ca²⁺ elevations are necessary for the transient effects of NO on cytosolic Cl⁻ levels, but the mechanism remains to be elucidated. Here, we investigated the involvement of TMEM16A as a possible link between Ca²⁺ elevations and cytosolic Cl⁻ release. TMEM16A is a Ca²⁺-activated Cl⁻ channel that is functionally coupled with CFTR in epithelia. Both proteins are also expressed in neurons. Based on this and its Ca²⁺ dependence, we test the hypothesis that TMEM16A participates in the NO-dependent elevation in cytosolic Cl⁻ in ACs. Chick retina ACs express TMEM16A as shown by Western blot analysis, single-cell PCR, and immunocytochemistry. Electrophysiology experiments demonstrate that TMEM16A functions in amacrine cells. Pharmacological inhibition of TMEM16A with T16inh-AO1 reduces the NO-dependent Cl⁻ release as indicated by the diminished shift in the reversal potential of GABA_A receptor-mediated currents. We confirmed the involvement of TMEM16A in the NO-dependent Cl⁻ release using CRISPR/Cas9 knockdown of TMEM16A. Two different modalities targeting the gene for TMEM16A (ANO1) were tested in retinal amacrine cells: an all-in-one plasmid vector and crRNA/tracrRNA/Cas9 ribonucleoprotein. The all-in-one CRISPR/Cas9 modality did not change the expression of TMEM16A protein and produced no change in the response to NO. However, TMEM16A-specific crRNA/tracrRNA/Cas9 ribonucleoprotein effectively reduces both TMEM16A protein levels and the NO-dependent shift in the reversal potential of GABA-gated currents. These results show that TMEM16A plays a role in the NO-dependent Cl⁻ release from retinal ACs.

R, Patel PH, Bazan DZ, Mora A, Samuel N, Mingle AC, Leon LR, Varon J, Surani S. Drug-Induced Hyperthermia Review

Humans maintain core body temperature via a complicated system of physiologic mechanisms that counteract heat/cold fluctuations from metabolism, exertion, and the environment. Overextension of these mechanisms or disruption of body temperature homeostasis leads to bodily dysfunction, culminating in a syndrome analogous to exertional heat stroke (EHS). The inability of this thermoregulatory process to maintain the body temperature is caused by either thermal stress or certain drugs. EHS is a syndrome characterized by hyperthermia and the activation of systemic inflammation. Several drug-induced hyperthermic syndromes may resemble EHS and share common mechanisms. The purpose of this article is to review the current literature and compare exertional heat stroke (EHS) to three of the most widely studied drug-induced hyperthermic syndromes: malignant hyperthermia (MH), neuroleptic malignant syndrome (NMS), and serotonin syndrome (SS). Drugs and drug classes that have been implicated in these conditions include amphetamines, diuretics, cocaine, antipsychotics, metoclopramide, selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), and many more. Observations suggest that severe or fulminant cases of drug-induced hyperthermia may evolve into an inflammatory syndrome best described as heat stroke. Their underlying mechanisms, symptoms, and treatment approaches will be reviewed to assist in accurate diagnosis, which will impact the management of potentially life-threatening complications.

The pharmacology of the TMEM16A channel: therapeutic opportunities

The TMEM16A Ca²⁺-gated Cl^- channel is involved in a variety of vital physiological functions and may be targeted pharmacologically for therapeutic benefit in diseases such as hypertension, stroke, and cystic fibrosis (CF). The determination of the TMEM16A structure and high-throughput screening efforts, alongside ex vivo and in vivo animal studies and clinical investigations, are hastening our understanding of the physiology and pharmacology of this channel. Here, we offer a critical analysis of recent developments in TMEM16A pharmacology and reflect on the therapeutic opportunities provided by this target.